Field of Endeavor
The present invention relates to treating aneurysms and more particularly to a shape memory polymer foam device for treating aneurysms.
State of Technology
U.S. Pat. No. 8,133,256 for shape memory polymer foams for endovascular therapies provides the state of technology information quoted below.
“In the general application, a vascular anomaly is treated using the device with the intent of stabilizing the anomaly from further expansion and possible rupture. The device is delivered endovascularly to the site for therapy via a catheter. The catheter may be previously placed using a conventional guidewire or the device may be installed using the guidewire. Once the catheter is placed near the therapeutic site, the device is placed into the anomaly with the guidewire and guided visually by radiology. The device is then held in place and the foam is actuated to expand, filling the anomaly. Once expanded, the foam will stay in place on its own or an additional aid will be used to hold it in place; for example, a diaphragm for the aneurysm or a stent for the AVM. The foam is released from the guidewire or catheter via the expansion process or following actuation by known techniques. The guidewire and/or catheter is then retracted and the therapy is completed. Should there be a misplacement of the foam, retrieval is possible using another shape-memory polymer device or other conventional techniques.”
“Shape-memory materials have the useful ability of being formable into a primary shape, being reformable into a stable secondary shape, and then being controllably actuated to recover their primary shape. Both metal alloys and polymeric materials can have shape memory. In the case of metals, the shape-memory effect arises from thermally induced solid phase transformations in which the lattice structure of the atoms changes, resulting in macroscopic changes in modulus and dimensions. In the case of polymeric materials, the primary shape is obtained after processing and fixed by physical structures or chemical crosslinking. The secondary shape is obtained by deforming the material while is an elastomeric state and that shape is fixed in one of several ways including cooling the polymer below a crystalline, liquid crystalline, or glass transition temperature; by inducing additional covalent or ionic crosslinking, etc.”
“While in the secondary shape some or all of the polymer chains are perturbed from their equilibrium random walk conformation, having a certain degree of bulk orientation. The oriented chains have a certain potential energy, due to their decreased entropy, which provides the driving force for the shape recovery. However, they do not spontaneously recover due to either kinetic effects (if below their lower Tg) or physical restraints (physical or chemical crosslinks). Actuation then occurs for the recovery to the primary shape by removing that restraint, e.g., heating the polymer above its glass transition or melting temperature, removing ionic or covalent crosslinks, etc. Other types of polymers which undergo shape memory behavior due to photon induced conformational transformations, conformational changes (e.g., rod-coil transition) due to changes in chemical environment (pH, ionic strength, etc.), or structural changes due to imposed fields (e.g., electric, magnetic, . . . ) may also be used. Both shape memory alloys (SMAs) and shape memory polymers (SMPs) can be used for the shape memory material of the present invention.”
“A shape memory material therapeutic device has advantages over existing therapeutic devices of being able to be moved more easily through the catheter to the point of placement, A shape memory material therapeutic can be placed more precisely within the geometry of the vascular disorder, and there is a higher degree of control over the expansion process while the device was being held in the desired position. A shape memory material therapeutic can be controllably expanded while being held in precise placement. A shape memory material therapeutic expands to its secondary shape within a few seconds, which is much faster than current expandable hydrogel based devices. The modulus of the devices can be accurately controlled so that expansion forces are low and no damage is done to areas of the vascular lumen.
The shape memory material device is expandable from 100% to 10000% by volume. The shape memory material device is actuated by one of several means including electromagnetic energy delivered optically. The shape memory material device is used to occlude part or all of a lumen, aneurysm, artiovascular malformation, or other physical anomaly.”